"He was waving it around. He aimed it at a student, and then he pulled it, and then the teacher stepped in front of her -- the student that he aimed it at. And she was like, 'Put the gun down. Please put the gun down,'" student eyewitness Devin Harmon said.

"I was thinking that any of my friends could die and that I could die. Like I felt like if I breathed or something, that I would get shot," student eyewitness Marnada Bradagan said. "(The teacher) lunged toward him, bent his hand back and smacked it out of his hand and yelled, 'No!' and had him in an arm lock, I think," Bradagan said.

Baltimore County Police Chief James Johnson said the boy rode a school bus to school carrying a .25-caliber semiautomatic handgun.

"This weapon is small enough to fit in the palm of your hand; as large as the cellphone you have in your pocket," Johnson said. "He also carried a 6- to 7-inch hunting knife with him. The gun was loaded."

Johnson said at the end of first period, the boy pulled out the gun and pointed it at his teacher and classmates -- 25-27 students -- before pointing it at himself.

He said students fled the classroom, and the teacher physically intervened and managed to disarm the teen.

"We know that the teacher (who was a few feet away) immediately reacted," Johnson said. "The gun fell to the floor. The educator continued to restrain the young man and then summoned help with a hand-held radio issued to all teachers in Baltimore County schools."

The student was taken into custody, and the school was placed on lockdown for a short time while Baltimore County police conducted a limited search.

Parents rushed to the school after receiving a phone call from school administrators.

"Who knows what could've happened in here. It's any school though, and I don't know how they are going to change that regardless; inside of the school or outside of the school," parent Tammie Superczynski said.

School officials said students were not dismissed early; however, parents at the scene told 11 News police allowed parents into the building to pick up their children. Parents also told 11 News police had not closed any roads around the school and the situation was under control as the school resumed its normal activities.

School and county administrators praised the teacher, whom they did not immediately identify by name, for putting her life on the line, protecting her students and helping to avoid a tragedy.

"Teachers don't think of their personal safety first. They think of the safety of the student, and again, one of our teachers acted heroically," Baltimore County Executive Kevin Kamenetz said.

Johnson, Kamenetz and School Superintendent Dallas Dance held a news conference at 2 p.m. to discuss the incident in greater detail.

"Our schools are safe, not only for today, but also for tomorrow," Kamenetz said.

Kamenetz said an increased police presence at schools will begin, and officers will be equipped with handheld scanning devices for suspicious situations.

"Our schools are indeed safe," Dance said.

"Teachers want to teach, and our students want to learn. We share these same goals, and we're committed as a county to make that happen," Kamenetz said.

During the news conference, Johnson showed several weapons, including one similar to the one used at Stemmers Run. He emphasized gun safety and locking up weapons.

Johnson said the cost of gun locks range from $3 to $6 and showed several examples.

"If we find out through our investigation that the weapon was unsecured, we will charge whoever's responsible for that weapon," Johnson said.

Johnson said they have the boy in custody, and he will be charged as a juvenile. Police said his name will not be released.

Police said they are not sure yet how the student obtained the weapon or what his motive may have been.

"The bottom line is it's a school with children. It comes down to safety. Plus, it comes down to the parent monitoring your child. How does a 13-year-old get a gun and bring it to school?" parent Chris Presley said.

Police said the child's grandfather, 70-year-old Norman James Gatewood, is the owner of the .25-caliber handgun used in Tuesday's incident. Police said a summons was served and Gatewood was charged with violating the law that required gun owners to secure loaded firearms from children 15 years old and younger.